1939 to 1941: Investigating Nuclear Weapons

1939 to 1941: Investigating Nuclear Weapons

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March 1941

The Department of Terrestrial Magnetism (DTM) at the Carnegie Institution measures the fast cross-section of uranium-235. Using it, Rudolf Peierls, on the MAUD Committee, calculates a new critical mass for uranium-235 at 18 pounds as a bare sphere or 9 to 10 pounds when surrounded by a reflector. A memorandum is prepared by the MAUD Committee describing the importance of fast fission for bomb design and transmits it to the U.S. Briggs locks up the document on arrival and shows it to no one.

December 1940

The MAUD Committee issues a report on isotope separation authored by Franz Simon. The report concludes that manufacturing uranium-235 by gaseous diffusion is feasible on a scale suitable for weapons production.

July 1, 1940

The newly founded The National Defense Research Committee, headed by Vannevar Bush, takes over responsibility for uranium research. In his final report, Lyman Briggs requests $140,000 for further work: $40,000 for lab measurements, and $100,000 for large scale uranium-graphite studies. Bush approves only $40,000.